As the trend has pushed semiconductor devices to smaller and smaller sizes, different patterning techniques have arisen. These techniques include spacer defined quadruple patterning, extreme ultraviolet lithography (EUV), and EUV combined with Spacer Defined Double patterning. These approaches have allowed production of nodes in the 7 nm range.
Directed self-assembly (DSA) has been considered as an option for future lithography applications. DSA involves the use of block copolymers to define patterns for self-assembly. The block copolymers used may include poly(methyl methacrylate) (PMMA), polystyrene, or poly(styrene-block-methyl methacrylate) (PS-b-PMMA). Other block copolymers may include emerging “high-Chi” polymers, which may potentially enable small dimensions.
DSA can be used to form parallel lines or regular arrays of holes/pillars/posts with very small pitch and critical dimensions. In particular, DSA can define sub-20 nm patterns through self-assembly, while guided by surface topography and/or surface chemical patterning. As a result, a DSA polymer layer can be infiltrated with a precursor, or a film may be deposited selectively on one of the polymers of the DSA layers.
However, the DSA technique has several drawbacks. In particular, DSA polymers, such as PMMA or polystyrene, have low etch resistance. This makes the transfer of the pattern to layers below more difficult. The issue of low etch resistance becomes greater when the advanced polymers needed to further downscale the size of the semiconductor device has an even lower etch resistance and etch selectivity. In addition, the DSA may result in a high line edge roughness in the obtained patterns. Another drawback is that the obtained structure of parallel lines or array of holes may have some defects at random locations.
As a result, a method for selectively forming a film with higher etching resistance and etching selectivity is desired.